L-Arginine Supplementation Boosts Amino Acid Digestibility in Heat-Stressed Pigs

Heat stress is a persistent challenge in pig production, and its effects begin in the gut. Damage to the small intestinal epithelium during heat stress exposure impairs protein digestion and the absorption of amino acids, the building blocks that growing pigs need for muscle growth and maintenance. A new study tested whether supplementing diets with the amino acid L-arginine could counteract some of this damage, and the results point to measurable benefits in both digestibility and absorption.

The experiment, published as an open access original article in the journal Amino Acids, used 12 ileal-cannulated growing pigs with an average body weight of 27.0 plus or minus 3.1 kilograms. All animals were housed under heat stress conditions, with ambient temperatures ranging from 28.9 to 39.3 degrees Celsius during the trial.

The pigs were randomly assigned to one of two treatments. The HS-B group received a wheat and soybean meal basal diet, while the HS-Arg group received the same basal diet supplemented with 0.20 percent free L-arginine. Each pig received its assigned diet for five days, followed by two days of ileal content collection. To assess absorption, the team measured serum concentrations of free amino acids in blood samples taken two hours after feeding, using this postprandial measurement as an indicator of how much amino acid was being taken up from the gut into the bloodstream.

The heat challenge was substantial. Intestinal temperature rose by up to 1.6 degrees Celsius during the peak ambient temperature hours compared with the lowest ambient temperature recordings, confirming that the animals experienced meaningful thermal strain during the collection period.

The supplementation produced a clear shift in the flow of amino acids through the terminal ileum. The total flow of arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, and cysteine through the terminal ileum was reduced in the HS-Arg pigs, a statistically significant difference at P less than 0.05. The flow of threonine, valine, alanine, and serine also tended to be lower, at P less than 0.10. Lower ileal flow of an amino acid generally indicates that more of it disappeared from the digesta before reaching the end of the small intestine, which in this context points to greater digestion and absorption rather than losses.

Digestibility figures supported that interpretation. The apparent ileal digestibility of arginine, histidine, leucine, phenylalanine, tryptophan, and cysteine increased significantly in the HS-Arg pigs, while the digestibility of lysine, valine, and serine tended to increase at P less than 0.10.

The serum data added a second line of evidence. Concentrations of free arginine, histidine, isoleucine, lysine, methionine, valine, cysteine, glutamine, glutamate, glycine, proline, ornithine, and urea were all higher in the blood of HS-Arg pigs at P less than 0.05.

The authors concluded that supplemental arginine in diets for pigs exposed to heat stress conditions increased the apparent ileal digestibility and the serum concentrations of most essential amino acids. Because supplemental arginine appears to partially recover the integrity of the small intestinal epithelium, the findings suggest that the improved digestibility may be linked to better gut barrier function under heat stress, although the study design measured digestibility and serum amino acids rather than directly confirming a mechanism.

Several practical considerations follow from the trial parameters. The dose tested was modest, 0.20 percent free L-arginine added to a wheat and soybean meal basal diet, and the supplementation period was short, five days before two days of collection, in pigs weighing around 27 kilograms. The study was conducted under controlled heat stress conditions with a small number of cannulated animals, so the results describe acute responses in this specific setting rather than long-term growth or production outcomes.

For nutritionists working in warm climates, the study offers a targeted nutritional strategy: during periods of heat exposure, arginine supplementation was associated with improved ileal digestibility of most essential amino acids and higher postprandial serum amino acid levels in growing pigs. The work was published on 29 October 2026 as an open access article, allowing full access to the methods and results for readers who want to examine the treatment details in depth.

Subject of Research: The effect of L-arginine supplementation on amino acid digestibility and serum amino acid concentrations in growing pigs exposed to heat stress

Article Title: Effects of L-arginine supplementation on ileal digestibility of amino acids and serum concentrations of free amino acids in growing pigs exposed to heat stress conditions

Article References: Cervantes-Ramírez, M., Valle-Fimbres, J. A., Castillo-Luna, G., González-Aragón, F., Hernández-Coronado, A. C., Arce-Vázquez, N., Htoo, J. K., & Morales-Trejo, A. (2026). Effects of L-arginine supplementation on ileal digestibility of amino acids and serum concentrations of free amino acids in growing pigs exposed to heat stress conditions. Amino Acids. https://doi.org/10.1007/s00726-026-03569-3

Image Credits: AI Generated

DOI: 10.1007/s00726-026-03569-3

Keywords: heat stress, L-arginine, pigs, amino acid digestibility, ileal digestibility, serum amino acids, swine nutrition, small intestine, animal science, Amino Acids journal, Effects, supplementation